As increased digging force is applied to the holder of a digging tooth, the tooth eventually is forced to enter the ground and excavate material or otherwise, the tooth breaks. Usually, before the tooth can be broken, maximum power from the excavating machine is achieved or alternatively, the formation permits the tooth to penetrate and excavate, so the tooth usually survives. Sometimes the power applied to the tooth is insufficient to break the tooth and sometimes the geological strata is too soft to cause the tooth to break, so digging proceeds in an orderly manner.
Most digging teeth can be broken somehow or another, as for example lifting the bucket high into the air and dropping it from a great height in an attempt to clean the bucket. Should the bucket teeth strike a hard surface under these conditions, some teeth invariably will not have the structural integrity required to endure this mistreatment and they break.
A unitary digging tooth that is directly attached to the bucket lip is most likely not to break as compared to a tooth which is removably received within a pocket. It would therefore be desirable to have a tooth of unitary construction which is directly welded onto the lip of a bucket, for example, so that the tooth could exhibit great strength that is directly proportional to its cross-sectional area, composition of material, and geometrical configuration. Such a design would provide a very strong tooth of great durability; however, the tooth would be impractical for most excavating machines because digging teeth sometime must be replaced after only a few hours of use; and, therefore, it would be necessary to replace the entire tooth assembly, or alternatively, have made available a bucket lip that was replaceable such as shown in U.S. Pat. Nos. 848,743 and 2,660,323.
The present invention provides a digging tooth assembly comprised of a digging tooth and holder that resists breaking because of the unusual manner by which they are joined together. The tooth digs more efficiently because the unique configuration of the working end of the tooth is designed to enter hard formations with minimum applied force. Moreover, the design of the tooth causes the cutting edges thereof to remain in a condition for efficiently digging for a long time. The tooth of the present invention therefore transfers power applied from the excavating machine into the working end of the tooth in a superior manner. All of these desirable features of a digging tooth made in accordance with the present invention provides unusual and unexpected results.
In my previous U.S. Pat. No. 4,476,642, there is set forth a digging tooth and holder assembly made for either a trencher or a bucket. The present invention is an improvement over this prior patent because of the configuration of the working end of the tooth as well as the configuration of the shank and pocket therefor.